Offer ability to create "Pull Requests" in the wiki

When a user has made changes to a wiki page it would be nice to offer 2 possibilities:

• He/She clicks on "save" and the change is committed immediately (normal mode)
• He/She can click on a "Make Proposal" button and the change acts like a PR in GitHub. Two things would happen:
  • It's sent to some wiki moderator emails (could be a mailing list)
  • A page is created is created with the proposed changes (for review and cancel/acceptance) and a discussion can ensue (using annotations and comments) with the PR creator to discuss the change.

This would allow to solve the issue discussed at http://www.yesodweb.com/blog/2015/08/thoughts-on-documentation

WDYT?